How are decisions made by the
Los Angeles Fire Department to pre-deploy resources on days of high wildfire hazard?
The answer is science.
To learn more, we turn to Captain Daniel Curry, lead for the
LAFD Fire Weather Program, who explains...
The LAFD utilizes a Burning Index (BI) to determine the Department’s commitment to pre-deploy resources. A number of procedures occur daily to determine the BI.
First, dead fuel moisture readings are taken in the early afternoon at Fire Station 108 on Mulholland Drive, and communicated to LAFD's North Division office located at Fire Station 88 in the San Fernando Valley.
Second, a group of federal meteorologists at the
Southern California Geographic Coordination Center (SCGACC) in Riverside, California provide a "
fire weather forecast" consisting of a predicted high temperature, low relative humidity, wind speed and direction for the next day.
Third, historical data (high/low temperature, high/low relative humidity and hours of rainfall in the last 24 hours) is mixed into the brew.
All of this information is fed into equations that make up the
National Fire Danger Rating System (NFDRS). The result is the BI. Theoretically, fire danger is elevated when BI’s reach historically high values.
The
daily BI levels are stated as a numerical value:
BI 0 to 37 = Low
BI 38 to 47 = Moderate
BI 48 to 110 = High
BI 111 to 161 = Very High
BI 162 to 211 = Extreme
BI 212 and above = Critical
On
Extreme and
Critical days the Los Angeles Fire Department will pre-deploy resources into select
Neighborhood Fire Stations serving brush areas. The specific stations/locations selected for pre-deployment are based on fire experience, area access and fire potential.
Not all forecasts become reality, so LAFD North Division personnel conduct real-time weather surveys, monitor
Remote Automated Weather Stations (RAWS) in and near the City of Los Angeles and consult the
National Weather Service (NWS) to stay abreast of fire weather conditions and forecasts.
Conflicting information can occur in weather forecasting, depending on who you listen to. Radio and television weather forecasters are broadcasting to a wider community than the City of Los Angeles, and pass along information on "Red Flag Warnings", for instance, that may not apply to the LAFD and the area it serves.
The NWS and SCGACC may come to different conclusions on the forecast as well, based on which computer model each agency trusts. Ultimately, the LAFD must make decisions on pre-deployment based on all of these inputs – with a lot of experience mixed in.
Please note that LAFD uses the term "
Red Flag Alert" to indicate forecasted or existing "Red Flag" conditions inside the City of Los Angeles. A "Red Flag Alert" is called when the wind speed is 25 miles per hour or more and the relative humidity is 15% or less. History has proven that a combination of strong winds, low relative humidity and warm temperatures will create explosive fire growth potential.
For this reason, parking restrictions may exist on certain narrow streets in brush areas during “Red Flag” conditions. To determine current
Red Flag Parking Restrictions within the City of Los Angeles, please call 3-1-1 or visit:
lafd.org/redflag
Submitted by
Brian Humphrey, Spokesman
Los Angeles Fire Department